Polymer blends comprising polyolefins are known in the art. Various polymer blends comprising polyolefins are disclosed, for example, in Chundury et al., U.S. Pat. Nos. 6,911,492, 5,969,027, 5,321,081, and 5,264,280. Polyolefins such as polypropylene provide a lower cost alternative to engineering resins such as acrylonitrile butadiene styrene (ABS) polymer resins, and are thus used in a variety of applications including, for example, preparing parts for the automotive industry, for communication devices such as telephones, radios, televisions, cassettes, for power tools, for appliances and other household implements, for floor care products, for business machines, and in the manufacture of toys and furniture.
Glass fiber reinforced plastics compounds tend to have poor physical properties due to the use of rutile titanium dioxide in pre-colored compounds. Rutile titanium dioxide provides outdoor weathering stability, however. In liquid handling applications, burst pressure is a key property as well as weathering stability. As a white pigment, zinc sulfide (ZnS) does not cause as severe physical property degradation as TiO2, however ZnS becomes somewhat transparent after weathering, which allows other pigments to show through somewhat strongly, and change the observed color of an article so produced. This leads to compounds that can be darker after outdoor exposure. Zinc oxide (ZnO) provides UV stability, and does not degrade physical properties as severely. However, three times as much ZnO is needed to achieve similar opacity as a given amount of ZnS. Anatase titanium dioxide causes less degradation than rutile TiO2, however after some exposure the materials become photoactive, leading to chalking (microcrazing) on the material's surface. A specially surface treated grade of anatase titanium dioxide was explored which, in conjunction with hindered amine light stabilizers, provide superior UV stability, without the loss of physical properties, particularly strength properties.